Residents off Melbourne's northern suburbs have been advised to stay alert and calm as a fast moving 200 hectare out of control grassfire could pose an immediate threat to lives and homes in the Wollert area.

The Country Fire Authority, on its Web site, said the fire is travelling in a southerly direction towards Vearings Road, Craigieburn Road East and Epping Road. It is expected to impact Epping and Wollert between 3.45pm and 4.30pm.

Emergency warnings have been issued for the Vearings Road and Craigieburn Road, Wollert area.

The fire is currently burning 27 kilometres north of the Melbourne CBD, which is close to the Hume Freeway.

Residents are advised to follow their bushfire survival plans.

"It's really of concern to us because it has the chance to run into some housing on the east of Craigieburn and the Hume Fwy," Kevin Monk, State Control Centre spokesman, said.

"At about 1.30pm it's just done a major run and burnt through about 200ha, which shows how serious the conditions are with strong winds and hot and dry conditions.''

"On days like today fires can just about start anywhere. It's so dry hot and windy across the west, it doesn't take much these days to get a fire going."